gistfile1.txt

/* Richard's Traffic Light Program */

int pinRedLed = 2;
int pinYelLed = 3;
int pinGrnLed = 4;
int lightState = 0;

void setup() {
    pinMode(pinRedLed, OUTPUT);    /* Set the LED pins to output */
    pinMode(pinYelLed, OUTPUT);
    pinMode(pinGrnLed, OUTPUT);
    digitalWrite(pinRedLed, HIGH);  /* Turn the RED light on, so we don't cause any traffic accidents while we initialise <img src="http://s.wordpress.com/wp-includes/images/smilies/icon_smile.gif" alt=":)" class="wp-smiley">  */
}

void loop() {

    lightState++;
    if (lightState > 3) {            // If the light state > 3, reset it to 0 (red).
      lightState = 0;
    }       

  delay(2500);

  /* Display correct light sequence */
  if (lightState == 0) { // Red
    digitalWrite(pinRedLed, HIGH);
    lightOff(pinYelLed);
    lightOff(pinGrnLed);
  }
  if (lightState == 1) { // Red and Amber
    digitalWrite(pinRedLed, HIGH);
    digitalWrite(pinYelLed, HIGH);
    lightOff(pinGrnLed);
  }
  if (lightState == 2) { // Green
    digitalWrite(pinGrnLed, HIGH);
    lightOff(pinYelLed);
    lightOff(pinRedLed);
  }
  if (lightState == 3) { // Amber-only
    digitalWrite(pinYelLed, HIGH);
    lightOff(pinRedLed);
    lightOff(pinGrnLed);
  }

}

void lightOff(int pin) {
  digitalWrite(pin, LOW);
}